The compressor pressure ratio of a gas turbine engine generally is set at a pre-specified margin away from the surge/stall boundary (referred to as a surge margin or a stall margin), to avoid unstable compressor operation. In gas turbine engines used for power generation and other purposes, higher system efficiencies generally require higher compressor pressure ratios. Such higher pressure ratios, however, may necessitate a reduction in the operating surge/stall margin and hence a reduction in the response time if surge or stall conditions begin to develop.
One approach to compressor surge or stall detection is to monitor the health of the compressor by measuring the airflow and the pressure rise through the compressor. These pressure variations may be attributed to a number of different causes such as, for example, unstable combustion, rotating stall, and surge events on the compressor itself. To determine these pressure variations, the magnitude and rate of change of the pressure rise through the compressor may be monitored. This approach, however, does not offer prediction capabilities of rotating stall or surge. Moreover, this approach may fail to offer information in real-time to a control system with sufficient lead time to deal proactively with such events.
There is thus a desire for improved systems and methods for surge event precursor detection and protection. Such system and methods may determine a measure of surge likelihood in the compressor before an actual surge event itself with sufficient lead time to respond adequately so as to avoid damage thereto.